错误原因：
在方法上写的属性名称为： [Authorize]

 [Authorize] 
 [HttpPost]
 [Route("api/xxxx/xxx")]
 public Message aaaa([FromBody] xxxx req)

自定义的过滤器为：

 public class ApiAuthAttribute : AuthorizeAttribute
   {
   }

解决办法：将 [Authorize] 改为 [ApiAuth]

 [ApiAuth]
 [HttpPost]
 [Route("api/xxxx/xxx")]
 public Message aaaa([FromBody] xxxx req)